My Galaxy S10+ is usually happy to share its video signal w my Westinghouse SmartTV; I plug in the HDMI adapter and I enjoy some Netflix. I believe I've also gotten Amazon Prime Video to work with it.
Now, if I try playing a video with either one of those services, I get the "Sorry, unable to load this video right now." That's been going on for a couple of days. I did a soft reset, optimized my device, got an alert that some apps had used too much storage space for temp files & that I should "Clear cache" for those apps, which I did.
Now Netflix works fine over HDMI. Prime Video does not, though it works fine when the phone's not HDMI-connected.